1. Field of the Invention
The invention relates to waterproofing leather by incorporating particular fatliquoring agents which import hydrophobic properties. The particular agents include sulfosuccinic acid monoester salts.
2. Statement of Related Art
Waterproof leather is produced by three basic methods, namely:
(1) impregnation by incorporation of water-insoluble substances, for example solid fats, waxes or particular polymers; PA1 (2) impregnation by incorporation of water-swelling substances which, on taking up water, form highly viscous emulsions and block the fiber interstices of the leather, for example special emulsifiers of the water-in-oil (W/O) type; and PA1 (3) treatment with hydrophobicizing substances, for example aluminium and chromium complexes, silicones or organic fluorine compounds.
These methods may be applied in the course of conventional fatliquoring using conventional fatliquoring agents, the impregnating and treatment agents mentioned being introduced into the fatliquoring bath.
A combination of methods (2) and (3) is often applied in practice, the drum or tumbler preferably being filled with aqueous liquor for economic and ecological reasons. The W/O emulsifiers are converted into hydrophobicizing metal salt complexes by fixing with chromium or aluminium salts. However, there are disadvantages to this process because, due to the instability of the fatliquoring emulsions normally used, impregnation has to be carried out at relatively high pH vaues (&gt;6) in order to avoid precipitation of the fatliquoring agents on the surface with resultant smearing. In addition, the fatliquoring bath generally has to have a high temperature of around 60.degree. C. in this process which loosens the grain of the leather. Furthermore, penetrometer values obtained in practice frequently show considerable variations due to an uneven distribution of fat through the leather, so that the leather may have to be expensively aftertreated by spraying, casting or plush coating.
The fatliquoring bath is not stabilized with anionic and nonionic emulsifiers, such as alkylsulfates, alkylarylsulfonates or fatty alcohol ethoxylates, because of the increase in permeability to water vapor.
As used throughout this specification, the term "leather" is meant to include skins, hides, and similar materials of animal origin to which hydrophobic properties are to be imparted.
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, or defining ingredient parameters used herein are to be understood as modified in all instances by the term "about".
Published German patent application No. 16 69 347 describes the use of sulfosuccinic acid esters emulsifiable in water for the fatliquoring of leather. In this case, however, no waterproofing effect is obtained.
Published German patent application No. 34 19 405 relates to a process for the production of leather in which a combination of sulfosuccinic acid esters with certain anionic or nonionic emulsifiers is used as fatliquoring agent in the tranning liquor during chrome or aluminum tanning or retanning. Once again, no waterproofing effect is obtained.